Owing to continuous increases in population and industrial development, oil is now the starting material for 95% of chemical products, and has become one of humanity's most important natural resources.
However, oil deposits are limited and there are many environmental issues associated with exploiting oil deposits. Thus, it is important to develop alternative solutions, and as a consequence, there are many investigations researching alternative materials to oil resources. In this regard, biomass (derived from plant resources such as corn, sugarcane, ligno(wood)-plant resources, palm, and algae), which is naturally produced, renewable, and environmentally (eco-) friendly, is regarded as an important potential resource for oil substitutes.
The automobile industry is closely associated with oil resources, and the importance of biomass-related research and development as future resources for the automobile industry is increasing.
Despite small industrial scale and lower economic efficiency than petrochemical material of biomass, recent report by Utretcht University (according to a request of European bio-plastic association and EPNOE (European Polysaccharide Network of Excellence)) expects that the usage of biomaterials will rapidly increase ten (10) years from now, and that up to 90% of petrochemical materials can be substituted with biomaterials. Examples of inner/outer injection unit materials currently used in the automobile industry include polypropylene, nylon, polycarbonate and Acrylonitrile butadiene styrene (ABS). Of the above materials, polypropylene is the most commonly used, and nylon is the second most commonly used (about 15 kg per automobile). Therefore, if the manufacturing technology for nylon were converted into that based on biomass, it is expected that considerable ripple effect would occur. As such, many research projects for biomass-based nylon materials are underway.
Among the various nylon materials, there is great demand for nylon 66 as well as nylon 6 because of their superior properties, but the manufacturing technology from biomass resources has not yet been established. Once manufacturing technology for nylon 66 has been developed, it is expected to have a huge effect in terms of both economic and environmental aspects.
Nylon 66 is used for automobile parts that can withstand high temperature because of its excellent heat resistance, abrasion resistance, and chemical resistance. After nylon 6, it is the most frequently used nylon for automobiles. Nylon 66 is prepared by the dehydration condensation reaction of hexamethylenediamine and adipic acid. Monomeric adipic acid for nylon 66 synthesis is produced via a chemical synthetic process using cyclohexanone derived from benzene which is obtained in the purification process of crude oil.
However, the above manufacturing technology and process have many problems such as oil price instability, the usage of toxic compounds such as benzene, and the formation of environmental pollutants including NOX. Thus, there is a need to substitute this current manufacturing technology with biomass technology. Accordingly, nylon production using biomass will decrease oil dependency and reduce the formation of environmental pollutants.
In the nylon 66 production using biomass, synthesizing adipic acid for the nylon 66 monomer from biomass is considered the most important step. However, this technology remains at the research and development (R&D) stage, and has not yet been commercialized. In addition, technologies for synthesizing adipic acid from glucose or galactose have not yet been disclosed, though there are several patents using glucaric acid as an intermediate for adipic acid synthesis.
Specifically, a method for preparing D-glucaric acid derived from green algae has been applied. D-glucaric acid is prepared using green algae-derived sugar, and specifically, D-glucuronic acid is converted from primitive forms of green algae into D-glucaric acid by using a recombinant microorganism transfected with the D-glucaric acid production gene. This method comprises steps of (i) drying and milling green algae to form green algae particles; (ii) hydrolyzing the green algae powder with an acid catalyst to obtain monosaccharide; and (iii) converting the monosaccharide into D-glucaric acid by fermentation with a recombinant microorganism having the D-glucaric acid production gene. Here, a novel fermentation process for preparing a chemical product with enormous industrial utility by using green algae resources, but it has not been implemented on an industrial scale. The process is very complicated because it uses metabolic engineering technology for glucaric acid production by utilizing (i) saccharification technology to prepare monosaccharide from primitive forms of green algae and (ii) a recombinant microorganism for the production of glucaric acid.
Other research regarding D-glucaric acid production from biomass includes Moon, T. S. et al. (Moon, T. S. et al. (2009) Appl. Environ. Microbiol. 75: 589-595), which discloses a method for D-glucaric acid production using D-glucose as raw material.
In the above method, D-glucaric acid is prepared via a complex chain enzymatic reaction in Escherichia coli by using PPS (phosphoenolpyruvate synthase), myo-inositol-1-phosphate synthase, phosphatase, myo-inositol oxygenase, and urinatedehydrogenase. This is a very complicated synthesis, and efficiency with the glucose input is very low (yield: 17.4% or less).
Further, a biological method for preparing adipic acid and adipic acid from renewable fatty acids and a genetically modified microorganism such as yeast has been developed.
Genetic modification for adipic acid production with high yield for preparing adipic acid in which genetically modified yeast comprises PDX5 polypeptide wherein PDX4 polypeptide or its promotor, FAT1 polypeptide or its promotor and ACS1 polypeptide gene are removed, and a method for producing adipic acid from fatty acid resources via fermentation have been studied.
However, the above technologies are much more complicated than chemical synthetic methods, and their costs are very high.
Under the above circumstances, the present disclosure describes a novel synthetic method which can simply and economically provide adipic acid from biomass such as plant or marine resources. Further, the present disclosure describes a method comprising preparing glucaric acid or galactaric acid as an intermediate from glucose or galactose derived from plant or marine resources, and then reducing this intermediate to form adipic acid, providing a bio-adipic acid synthesis with a simple and eco-friendly process and a low cost, thereby completing the present disclosure.